The proposed research is intended to investigate the immune capabilities of inbred birds infected with the lymphatic-dwelling parasite Brugia pahangi. The studies are designed further to define the regulatory influences exerted by and on the immune system during the course of infection with filariasis and to relate these influences to the development of infection. Particular attention will be directed toward evaluating the relationship of the responsiveness of lymphoid cells, responsible for cellular and humoral immunity, to the expression of patency as detected by the presence of microfilaria. Assessment of immunologic reactivity will be facilitated by determination of in vivo antibody production, histopathological analysis of lymphoid tissue and primarily by in vitro methods of production of antibody, blastogenesis and soluble immune regulatory factors. The information derived from these studies should provide a clearer understanding of the immune mechanisms which are operative during filariasis, the role of immune mechanisms in expression of the disease and the potential for immunologically controlling infection with filariasis.